1. Field of the Invention
The present invention relates generally to implantable medical devices, and more particularly, relates to implantable medical devices for the treatment of obstructive sleep apnea.
2. Description of the Prior Art
The medical characteristics of sleep apnea have been known for some time. There are two generally recognized forms of the disease. The first is central sleep apnea which is associated with the failure of the body to automatically generate the neuro-muscular stimulation necessary to initiate and control a respiratory cycle at the proper time. Work associated with employing electrical stimulation to treat this condition is discussed in "Diaphragm Pacing: Present Status", by William W. L. Glenn, in Pace, Volume I, at pages 357-370 (July - September 1978).
The second condition is known as obstructive sleep apnea. It is discussed at some length in "Obstructive Sleep Apnea: Diagnosis and Treatment", by Drs. Cook and Osguthorpe in Journal of South Carolina Medical Association, 81 (12): 647-651 (December 1985).
At present, a tracheostomy may be the treatment of choice for a number of patients when obstructive sleep apnea is severe, although systems employing continuous positive air pressure (CPAP) are now available. However, some interest has been displayed in electrical stimulation of the muscle tissue along the upper airway during respiration. U.S. Pat. No. 4,830,008 issued to Meer discusses a technique for electrical stimulation of the muscles of the upper airway in synchrony with the respiratory cycle. U.S. Pat. No. 4,506,666 issued to Durkan discusses such stimulation in conjunction with pressurized airflow supplied by a respirator.
As with most chronically implantable electrical stimulation systems, those directed to the treatment of obstructive sleep apnea have an implantable pulse generator remotely located from and cabled to sensors and stimulation electrodes. For the treatment of obstructive sleep apnea, this means that the implantable pulse generator is preferably located in the torso of the patient and one or more sensors and/or stimulation electrodes are located in the head. This configuration necessitates cabling which traverses the neck region.
Currently available insulated leads for cabling implantable pulse generators to sensors and electrodes tend to be cylindrical in shape and optimized for flex strength. Such insulated leads tend to produce an undesirable bulge in the neck region of patients having implantable obstructive sleep apnea stimulation systems.